Best Time to Transplant Hibiscus Plant

My in-laws have had a Hibiscus plant growing outside of their garage for many years. We are selling the house and we want to move the Hibiscus plant to a new home. When is the best time of year to move it and how should I move it? Dig it out with a ball of soil attached or just uproot it and move it? I live in western Pennsylvania with cold winters and mild springs and fall.